The heart is responsible for circulating blood throughout the body. The heart includes four chambers: the left atrium (“LA”); the right atrium (“RA”); the left ventricle (“LV”); and the right ventricle (“RV”). Blood that has circulated through the body enters the RA, flows into the RV, and out of the heart to the lungs. Oxygenated blood from the lungs enters the LA, flows into the LV, and out of the heart to the various organs of the body. A normal heart rhythm is associated with electrical and mechanical activity corresponding to the atrial and ventricular contractions. A normal cardiac cycle includes systole (contraction of the ventricles causing blood to move through the body) and diastole (relaxation of the ventricles during which the ventricles fill with blood). Thus, when a ventricle fills, the corresponding atrium empties its contents into the ventricle.
A normal heart rhythm results in an efficient pumping of blood throughout the body. In this regard, the atrioventricular contractions must be properly timed to enable the transfer of blood between the chambers of the heart. Normal hearts generate the electrical signals necessary to regulate the atrioventricular timing and heartbeat. A number of disorders, however, can adversely impact the operation of the heart. Medical devices, such as pacing systems, provide electrical stimuli to the heart in an attempt to correct an abnormal rhythm and/or to maintain a normal rhythm.
The prior art includes many different types of implantable medical devices (“IMDs”), such as pacing systems, cardiac resynchronization therapy devices, defibrillators, and the like. A given IMD may have a number of adjustable electrical and/or mechanical parameters associated with diagnostic or therapeutic functions, and such adjustable parameters may be regulated by the IMD using suitable control techniques. For example, a dual-chamber pacing device typically controls the atrioventricular (“AV”) delay in a manner that strives to optimize cardiac performance. Known adjustment techniques often rely upon empirical or historical data, or are based upon the heart rate or activity level of the patient. Another known technique uses an open loop feedback system having a separate device (typically an external device) that obtains and processes physiologic data from the patient. The physiologic data is analyzed by the separate device, and the IMD is reprogrammed if necessary. Such open loop systems, however, can be cumbersome, inconvenient, and expensive to use.
Accordingly, it is desirable to have technique for controlling IMD parameters in a closed loop manner. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.